The present invention relates to a surveillance system for monitoring traffic speed, and for recording and reporting speed limit violations.
Each motorized vehicle contains a transceiver for radio communication with a plurality of monitor transceivers fixed along a highway and/or mounted in police patrol cars. The monitor transceivers are coupled through conventional telephone lines, radio communication or the like, to a central processor which can be accessed by the motor vehicle department or other authorities. The vehicle transceiver communicates with the speedometer or other velocity detector for determining vehicle speed. The vehicle transceiver includes a preset codable input which is coded with the vehicle license number or other vehicle identification, and may be entered and accessed only by authorized personnel, such as the motor vehicle department. The vehicle transceiver also includes a second preset codable input which is selectively insertable by a driver by way of a magnetically readable card, keyboard entry, or the like, and contans driver identification such as social security number, driver's license or the like, and may have a plurality of authorized codes according to the number of authorized drivers. These codes are a conditon precedent to vehicle operation.
The monitor transceivers broadcast information including the speed limit for the given locale. The vehicle transceiver compares the received speed limit information against vehicle speed. A visual and/or audio warning may be given to the driver if the differential is below a set threshold. If the vehicle speed exceeds the speed limit by an amount greater than the given threshold, then a violation communication is issued. The vehicle transceiver sends speed limit violation information to the monitor transceiver, including the driver's identity by social security number or the like, and the vehicle identity, by license number or the like, together with the speed of the vehicle.
A self-contained tamper unit is provided in the vehicle transceiver separate from but communicating with the vehicle surveillance computer in the vehicle. The tamper system checks proper operation of the vehicle surveillance computer and various peripherals such as the speedometer, run enable circuitry to the engine, and the like, for securing against tampering or other defeating of the system, by preventing operation of the vehicle and/or by issuing a tamper alarm signal. Tamper events are stored in a separate nonvolatile memory for later verification and corroboration, and apprehension if appropriate. The tamper system also monitors engine RPM and the gear to check the integrity of the speedometer within given limits. When the vehicle transceiver is transmitting, the tamper system checks the standing wave ratio at the transmission antenna to determine proper transmission. The tamper system checks for proper operation of the vehicle surveillance computer by measuring the amount of time the vehicle surveillance computer takes to send a signal to the tamper system, and if the time is too short or too long, improper operation is detected. If any of these and various other checks signifies failure of one or more components, the tamper system records such event and optionally disables operation of the vehicle.
The vehicle transceiver continuously listens for the command frequency from monitor transceivers. The monitor transceivers may continuously transmit speed limit and vehicle reply commands, or may start to transmit such commands only when a vehicle is detected. When the vehicle transceiver detects command signals from the monitor transceiver, a delay may be initiated, at the end of which the vehicle listens for transmissions from other vehicles, and if such are detected, the vehicle restarts its delay and listens again at the end thereof, and repeats the sequence until there is clear air space for responding to the monitor transceiver. This prevents multiple responding transmissions from the vehicles to the monitor transceiver which would cause garbled interference. Multiple frequencies may of course be used, though a single reply frequency is desired for economy. The noted delay reduces the probability of simultaneous transmission by several vehicles back to the monitor transceiver. In one form, a particular dedicated delay is provided for each vehicle by using the sum of the social security number digits for determining the delay. For example, the probability of two vehicle drivers having the same social security number sum is about three in ten thousand. The chance that these drivers would be in the same locality is extremely remote. In addition to the violation being transmitted to the monitor receiver, the violation is also stored in nonvolatile memory on-board the vehicle surveillance computer system for later retrieval and documented corroboration.
The system preferably operates on two frequencies. The first is the vehicle transmit frequency which is the same for all vehicles and which is the monitor receive frequency. The second frequency is the vehicle receive frequency which is the same for all vehicles and which is the monitor transmit frequency. The vehicle has a transmitter for the transmit frequency and a receiver for the receive frequency. The vehicle has a second receiver at the vehicle transmit frequency for carrier detection of other vehicle transmissions at the end of the noted particular vehicle reply delay. A second transmitter may be incorporated on a dedicated alarm or tamper frequency for transmission to the monitor transceiver which would then include a second receiver at the dedicated alarm frequency. The system preferably uses directional antennas.
A stationary or fixed pole type monitor transceiver receives all vehicle transmissions but records only the given speed limit violation and stores such data along with the time and date for subsequent transmission to a central processor or assigned authorities. This transmission may be via phone lines through an auto-dial modem, with re-dial if busy, or by radio transmitter operating at the violation collection frequency, or cable TV channels, or the like. If the monitor transceiver is of the type issuing reply commands to vehicles only when a vehicle is detected, the absence of a reply from a passing vehicle indicates improper operation and/or tampering with the vehicle's velocity surveillance system, and this information is immediately transmitted to a central processor or the given authorities. In addition, the monitor sends a signal to the vehicle that it is not operating properly, which if received is stored in nonvolatile memory in the tamper system of the vehicle. The monitoring transceivers may additionally or alternatively be mounted in police patrol cars.